U.S. patent application number 12/297123 was filed with the patent office on 2010-06-10 for printed circuit board element and method for producing the same.
Invention is credited to Gregor Langer, Markus Riester.
Application Number | 20100142896 12/297123 |
Document ID | / |
Family ID | 38293266 |
Filed Date | 2010-06-10 |
United States Patent
Application |
20100142896 |
Kind Code |
A1 |
Riester; Markus ; et
al. |
June 10, 2010 |
PRINTED CIRCUIT BOARD ELEMENT AND METHOD FOR PRODUCING THE SAME
Abstract
A printed circuit board element (1) with a substrate (2), with
at least one optoelectronic component (3) embedded in a
photopolymerizable optical layer material (5), and with at least
one optical waveguide (6) optically coupled with the former and
structured in the optical material by photon absorption, wherein a
prefabricated deflection mirror (4) embedded in the optical
material (5) and optically coupled with the optoelectronic
component (3) via the optical waveguide (6) is arranged on the
substrate (2), optionally together with a support (4').
Inventors: |
Riester; Markus;
(Seiersberg, AT) ; Langer; Gregor; (Wolfnitz,
AT) |
Correspondence
Address: |
LADAS & PARRY LLP
26 WEST 61ST STREET
NEW YORK
NY
10023
US
|
Family ID: |
38293266 |
Appl. No.: |
12/297123 |
Filed: |
May 8, 2007 |
PCT Filed: |
May 8, 2007 |
PCT NO: |
PCT/AT2007/000217 |
371 Date: |
January 25, 2010 |
Current U.S.
Class: |
385/88 ;
29/829 |
Current CPC
Class: |
G02B 6/138 20130101;
H05K 1/0274 20130101; G02B 6/4214 20130101; Y10T 29/49124 20150115;
G02B 6/43 20130101 |
Class at
Publication: |
385/88 ;
29/829 |
International
Class: |
G02B 6/36 20060101
G02B006/36; H05K 3/00 20060101 H05K003/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 8, 2006 |
AT |
A 791/2006 |
Claims
1. A printed circuit board element (1) with a substrate (2), with
at least one optoelectronic component (3, 4) embedded in a
photopolymerizable optical layer material (5), and with at least
one optical waveguide (6) optically coupled with the former and
structured in the optical material (5) by photon absorption,
characterized in that a prefabricated deflection mirror (4)
embedded in the optical material (5) and optically coupled with the
optoelectronic component (3) via the optical waveguide (6) is
arranged on the substrate (2).
2. The printed circuit board element according to claim 1,
characterized in that the deflection mirror (4) is arranged on the
substrate (2) together with a support (4').
3. The printed circuit board element according to claim 1,
characterized in that the deflection mirror (4) and/or its support
(4') comprise position marks (16', 18, 19-21) for controlling a
laser beam (13) during the structuring of the optical waveguide (6,
6').
4. The printed circuit board element according to claim 3,
characterized in that the deflection mirror (4) and/or its support
(4') comprise an upwardly facing reflective field (18) for
determining the height position during structuring.
5. The printed circuit board element according to claim 3,
characterized in that the deflection mirror (4), in the region of
its mirror surface (7), comprises marks (19, 20, 21) for
determining deviations of the mirror surface (7) from the desired
position and for controlling the laser beam (13) during the
structuring of the optical waveguide (6, 6') in order to ensure the
optimum guidance of a light beam in the optical waveguide (6, 6')
in front of and/or behind the deflection mirror (4).
6. The printed circuit board element according to claim 1,
characterized in that the deflection mirror (4) is applied on the
same substrate (2) which carries the optoelectronic component
(3).
7. The printed circuit board element according to claim 1,
characterized in that the deflection mirror (4) is glued to the
substrate (2).
8. The printed circuit board element according to claim 1,
characterized in that the deflection mirror (4) is made of a
silicon material, a thermoplast, a duroplast, glass or an
in-organic/organic hybrid polymer, including a metal coating.
9. The printed circuit board element according to claim 1,
characterized in that the deflection mirror (4) comprises a
prismatic body having a plane mirror surface (7).
10. The printed circuit board element according to claim 1,
characterized in that the deflection mirror (4) comprises a concave
mirror surface (7).
11. The printed circuit board element according to claim 1,
characterized in that a further optical waveguide (6') is optically
coupled with the deflection mirror (4) to guide within an optical
waveguide (6, 6') both a light beam impinging on it and a light
beam reflected by it.
12. The printed circuit board element according to claim 11,
characterized in that a focusing lens (22) is associated with said
further optical waveguide (6') in the region of the surface of the
optical material (5).
13. The printed circuit board element according to claim 12,
characterized in that the lens (22) is obtained in the optical
material (5) by photon absorption structuring.
14. The printed circuit board element according to claim 12,
characterized in that the lens (22') is obtained in the optical
material (5) by laser ablation.
15. The printed circuit board element according to claim 12,
characterized in that the lens (22') is obtained in the optical
material (5) by a molding or stamping process.
16. The printed circuit board element according to claim 1,
characterized in that the or at least one optical waveguide (6)
ends at a distance in front of the deflection mirror (4).
17. The printed circuit board element according to claim 1,
characterized in that the or at least one optical waveguide (6,
6'), preferably both optical waveguides, are guided as far as to
the deflection mirror (4).
18. A method for producing a printed circuit board element (1) with
according to claim 1, characterized in that the deflection mirror
(4) is attached to the substrate (2) and the photopolymerizable
optical material (5) is subsequently applied in layer form, whereby
the deflection mirror (4) is embedded in said optical material (5),
and that the optical waveguide (6) is then structured by photon
absorption, by directing the laser beam (13) onto the desired site
in the optical material (5) and relatively moving said laser beam
(13) and said substrate (2) along with said optical material
(5).
19. The method according to claim 18, characterized in that the
deflection mirror (4) is applied on the substrate (2) together with
a support (4').
20. The method according to claim 18, characterized in that the
deflection mirror (4) or support (4') is glued to the substrate
(2).
21. The method according to claim 18, characterized in that the
focusing and/or relative movement of the structuring laser beam
(13) is controlled by the aid of position marks (16', 18, 19-21)
provided on the deflection mirror (4).
22. The method according to claim 21, characterized in that
deviations (19-21) of the mirror surface (7) from the desired
position are detected by the aid of position marks and, as a
function thereof, the structuring laser beam (13) used for
structuring the optical waveguide (6) is controlled for an optimum
guidance of the light beam (13).
23. The method according to claim 18, characterized in that said
structuring of the optical waveguide (6) is stopped at a distance
in front of the deflection mirror (4).
24. The method according to claim 18, characterized in that the
optical waveguide (6) is extended directly as far as the deflection
mirror (4) during structuring.
25. The method according to claim 18, characterized in that two
optical waveguides (6, 6') are structured in the optical layer
material (5), namely one for a light beam impinging on the
deflection mirror (4) and one for the light beam reflected by
it.
26. The method according to claim 25, characterized in that a
focusing lens (22, 22') is produced in the optical material in the
region of the end of the one of the optical waveguides (6'), on the
surface of the optical material.
27. The method according to claim 26, characterized in that the
lens (22) is produced during structuring by photon absorption using
the laser beam.
28. The method according to claim 26, characterized in that the
lens (22') is produced by laser ablation.
29. The method according to claim 26, characterized in that he lens
(22') is produced by a molding or stamping process.
30. The method according to claim 18, characterized in that the
deflection mirror (4) is produced by molding and curing a moldable
material, e.g. an inorganic-organic hybrid polymer or a
thermoplastic material, on a support (4') made, e.g., of silicon,
glass, polymer like polyimide or polycarbonate.
Description
[0001] The invention relates to a printed circuit board element
with a substrate, with at least one optoelectronic component
embedded in a photopolymerizable optical layer material, and with
at least one optical waveguide optically coupled with the former
and structured in the optical material by photon absorption.
[0002] The invention further relates to a method for producing such
a printed circuit board element.
[0003] From WO 01/16630 A1, a multilayer printed circuit board
element is known, in which optoelectronic components, in particular
VCSEL components, are provided in connection with an optical
waveguide. There, the optical waveguide is formed by an area-like
optical waveguide layer arranged between buffer layers and within
which the laser beam emitted by the VCSEL component has to be
oriented by the aid of a deflection mirror. To this end, it is
necessary that a narrow, bundled laser beam be generated by the
VCSEL component and propagated by the deflection mirror. The
respective VCSEL component is incorporated in one of the buffer
layers adjacent the optical waveguide layer, whereas the planar,
obliquely arranged deflection mirror is provided in the waveguide
layer to deflect the emitted laser beam by 90.degree. into the
waveguide layer. With that mode of construction, the orientation of
the VCSEL component and the associated deflection mirror is
critical.
[0004] From EP 911 658 A1 and EP 1 312 948 A2, it is known to
provide waveguide structures including deflection mirrors on a
substrate, which deflection mirrors are arranged within a waveguide
structure on predetermined out-coupling sites. In detail, the
respective deflection mirror in that case is embedded in a liquid,
light-sensitive layer--either subsequent or prior to the attachment
of this layer--and, after this, the waveguide structure is produced
by exposure, with the material of the light-sensitive layer
hardening in the exposed area. The unhardened material of the
light-sensitive layer is then removed. Subsequently, a covering
layer comprised of a polymer having a refractive index differing
from that of the waveguide is deposited onto this structure. The
thus obtained structure is, hence, similar to that of the
previously described WO 01/16630 A1, involving the problems of a
critical component orientation and narrow beam guidance within the
waveguide structure. It is, in particular, disadvantageous that the
z-position (height position) of the waveguide can neither be
adjusted nor changed during the writing process. This results in
the disadvantage of a limited positioning range of the waveguide
relative to the respective component. The positioning of the
z-coordinate of the waveguide is, in fact, unavoidable if, for
instance, the waveguide is to be positioned relative to aspherical
deflection mirrors. If, for instance, compact waveguide structures
having three-dimensional courses are desired, these will only be
feasible, with the known technique, by extremely complex multi-step
processes. Furthermore, predetermined out-coupling sites are
required in that prior art, with lenses being provided on the
covering layer in those coupling sites; the deflection mirrors have
to be positioned relative to these lenses in a very precise
manner.
[0005] From WO 03/005094 A1, a technique for coupling to optical
waveguides embedded in printed circuit boards is, furthermore,
known, wherein the optical waveguides are produced in an optical
layer by an embossing process and light is coupled out by chamfered
and mirrored optical waveguide ends. For positioning, mechanical
guide marks are produced by the embossing process, which may serve
as guide holes for MT pins. That way of production is relatively
complicated, whereby, initially, the channels for the waveguides
are to be produced in a transparent carrier film and chamfers are
provided on the ends of the channels for the mirrors. After this,
the channels are filled to form the waveguides.
[0006] On the other hand, it has already been known to produce an
optical waveguide structure in an organic or inorganic
photopolymerizable optical material by photon absorption processes,
whereby the optical material, while being irradiated with photons,
is locally converted in a manner as to have a larger refractive
index than the original, unstructured optical material. This is
known in the context of optocoupler components, for instance, from
WO 01/96915 A2, WO 01/96917 A2 and U.S. Pat. No. 4,666,236 A.
Comparable waveguide structuring in a photopolymerizable optical
layer is known from WO 2005/064381 A1 in connection with a printed
circuit board element, the technique described there forming the
starting point for the present invention.
[0007] It is an object of the invention to propose a technique for
printed circuit board elements, by which it is feasible in a simple
manner to deflect light from the plane of an optical position in an
optical printed circuit board element for the purpose of coupling
the same out, or to couple light into the plane of this optical
position, wherein waveguide structuring is still to be
unproblematic while, in particular, not requiring any mechanical
waveguide finishing. Furthermore, the subsequent insertion and
orientation of the optical components are to be avoided so as to
allow for a simple, extremely precise mounting of the optical and
optoelectronic components in a printed circuit board element with
an integrated optical system.
[0008] To solve this problem, the invention provides a printed
circuit board element as characterized in claim 1 as well as a
method as defined in claim 18. Advantageous embodiments and further
developments are indicated in the dependent claims. The technique
according to the invention allows for the simple, yet highly
precise production of a printed circuit board element in which a
deflection mirror is embedded in the optical layer material for the
purpose of coupling light into the waveguide or coupling light out
of the waveguide. When producing such a printed circuit board
element, no mechanical waveguide finishing is required, and the
optical components and, in particular, also the deflection mirror
can be fixed to the substrate in advance, prior to the application
of the optical material in layer form and the structuring of the
waveguide. Thus, a mechanical finishing procedure of the printed
circuit board element as applied, for instance, for the purpose of
producing bores for vertically coupling light out can be obviated,
too. Moreover, it is of particular advantage that marks present,
for instance, on the deflection mirror (or on a deflection mirror
support) can be used when structuring the waveguide for the
orientation of the laser beam "writing" the waveguide. Besides, it
is possible without any problem to provide a light channel
perpendicularly upwards to the surface of the printed circuit board
element for coupling light in or out. In this respect, also the
enabled positioning of the waveguide in the z-direction is
particularly beneficial, yielding special advantages especially
when premounting deflection mirrors. The combination provided by
the subject matter of the invention, of a photon absorption method
and a prefabricated deflection mirror arranged on the substrate, as
a result, offers the advantageous option of fixing the z-position,
i.e. height, of the optical waveguide in the photon absorption
process, whereby it is additionally possible to write a waveguide
from the respective deflection mirror vertically upwards for
coupling light in or out, what has not been possible in the prior
art. Above all, no extremely precise positioning of the deflection
mirror is required, since a position control of the laser beam is
possible--e.g. via markers provided on the deflection mirror--when
writing the waveguide in the correct position. It is, furthermore,
possible to produce lenses only subsequently in the optical
material, with deviations of the position of the mirror being still
compensateable.
[0009] In the technique according to the invention for structuring
waveguides, a photon process known per se (e.g. two-photon
absorption--TPA) is applied, which activates a chemical reaction
(e.g. polymerization) by the simultaneous absorption of two or more
photons. In doing so, it is advantageous that, due to the
transparency of the optical material for the excitation wavelength,
any point within the volume can be reached so as to readily allow
for the writing of three-dimensional structures in the volume,
whereby very small focus ranges and, hence, very small structural
dimensions can, moreover, be achieved. Besides, the two-photon
process is a simple one-step structuring process.
[0010] In detail, when structuring the optical waveguide within the
optical layer, it may advantageously be proceeded in the manner
described in WO 2005/064381 A1, wherein the components already
embedded in the optical layer are targeted by a measuring light
beam using a camera or similar optical vision unit, and are
detected in terms of position; via this vision unit, a radiation
unit including a lens system is then controlled to move the focus
region of the emitted photon beam, in particular laser beam, in the
plane of the printed circuit board element, i.e. in the x/y plane,
on the one hand, and to adjust the same also in terms of depth
within the optical layer, i.e. in the z-direction, on the other
hand. Using the respective component as a reference element, the
optical waveguide can, thus, be structured in the desired fashion
within the optical layer, e.g. as a simple, linear optical
waveguide connection or also as a waveguide structure having
curvatures, junctions or similar structures and, in particular,
even as a three-dimensional structure. The cross-sectional
dimensions of the thus structured optical waveguide can, for
instance, range in the order of some micrometers, wherein the cross
section of such a structurized optical waveguide may be circular,
yet also elliptical or rectangular; the exact shape can be
determined by the photon beam and its focus control.
[0011] With the technique according to the invention, it is of
particular advantage that the deflection mirror (or a mirror
support) likewise embedded in the optical material may comprise
position marks for controlling the laser beam during the
structuring of the optical waveguide in order to ensure an accurate
guidance of the laser beam in the X/Y plane; above all, the
deflection mirror (or its support) may also comprise marks such as
an (optionally obliquely) upwardly facing reflective field for
determining the height position during the structuring of the
optical waveguide. The deflection mirror is preferably applied,
particularly glued, to the same substrate to which also the
optoelectronic component is attached. The deflection mirrors may be
set in the same operating step as the optically active components,
i.e. optoelectronic components such as, e.g. VCSEL components
and/or photodiodes, so as to ensure a particularly simple
production.
[0012] For the deflection mirrors, prefabricated silicon blocks
provided, for instance, with planar 45.degree.-inclined surfaces to
obtain a 90.degree. light deflection may be inserted. In addition
to silicon material, also glass, a thermoplast or a duroplast or
even an inorganic/organic hybrid polymer may be used for the
deflection mirrors, mirroring by a metal coating being feasible.
The deflection mirror, in particular, comprises a prismatic body
with a planar or concave, i.e. (a)spherical, mirror surface,
wherein, in the case of a slightly concavely configured mirror
surface, a focusing effect for the light beam will be achieved by
the concave-mirror shape.
[0013] It is, furthermore, favorable if, as already indicated
above, a further optical waveguide is optically coupled with the
deflection mirror in order to guide within an optical waveguide
both a light beam impinging on it and a light beam reflected by it,
i.e. the light beam is guided in the structured optical waveguide
both parallelly with the plane of the printed circuit board element
and perpendicularly thereto, in order to avoid possible light
losses during coupling-in and coupling-out proper. The optical
waveguide may, moreover, be structured in a manner as to not be
completely extended as far as to the deflection mirror, but to end
at a--small--distance in front of the same. This will, above all,
be the case where the deflection of the light to the surface of the
printed circuit board element is feasible without a waveguide path.
However, the present structuring of the optical waveguide by a
photon process readily enables the guidance of the deflection
mirror exactly as far as to the deflection mirror during
structuring. Furthermore, such structuring by a photon process also
renders feasible, in the event of an additional, vertical optical
waveguide leading to the upper side of the optical layer, to
structure on this upper side in the region of the end of the
optical waveguide a focusing lens in the optical material in order
to achieve an additional focusing of the light beam after its
reflection at the deflection mirror. Instead of using photon
structuring, such a focusing lens in the region of emergence of the
vertically upwardly leading optical waveguide can, however, also be
produced by removing material from the surface of the optical
material, for instance by laser ablation, such that a lens is
"burned" into the optical material. Another option consists in
producing the lens by a molding or stamping process, since the
optical material is still soft and moldable during the photon
structuring process.
[0014] The deflection mirror, instead of being machined by sawing
or grinding from silicon, glass or duroplasts (e.g. polyester,
cured epoxy resins, formaldehyde resins) as already mentioned, may
also be produced from materials suitable for molding processes,
wherein, for instance, UV-curing materials such as
inorganic-organic hybrid polymers, or thermoplastic materials such
as, e.g., polycarbonate, polymethylmethacrylate or polystyrene may
be employed. In this respect, it is, in particular, also
conceivable to simultaneously produce a plurality of deflection
mirrors on a support such as, for instance, a silicon wafer, on
glass, or on a support made of a polymer, e.g. polyimide, for
instance, according to the molding process as basically known from
EP 1 460 738 A, yet in the context of the production of
semiconductor components. This is a simple and cost-effective
option to produce a plurality of mirrors with planar, yet
optionally also spherical or aspherical mirror surfaces, the
remaining silicon wafers of the individual deflection mirrors
facilitating the handling and insertion of the components.
[0015] Hence results that, in the main, the present technique
renders feasible a printed circuit board element which is extremely
cost-effective to produce and with which the advantage of a
simultaneous insertion of the components, namely the deflection
mirror and, at the same time, other elements, e.g. the optically
active elements like laser components and photodiodes etc. is to be
regarded as particularly essential. Precise positioning of the
components is not necessary in this case, the components rather may
be attached using a commercially available SMT device. Waveguide
structuring will then take place in a subsequent step, the coupling
of the optical waveguide to the components being possible with an
extremely high precision based on the measurable positions of the
previously attached components, with deviations such as, for
instance, deviations in the angular positions or height deviations
being automatically compensateable during waveguide
structuring.
[0016] The printed circuit board elements according to the
invention enable multi-mode or single-mode data transfers at
extraordinarily high data transfer rates, and the invention may
advantageously be used with printed circuit boards, e.g.
optoelectronic backplanes or flex printed circuit boards, for cell
phones and other so-called handhelds.
[0017] In the following, the invention will be explained in more
detail by way of particularly preferred exemplary embodiments, to
which it is, however, not to be restricted, and with reference to
the drawing. In the drawing, in detail:
[0018] FIG. 1 is a schematic sectional view of a printed circuit
board element according to the invention comprising an
optoelectronic component and a deflection mirror attached to the
same substrate at a distance from the former;
[0019] FIGS. 2, 3 and 4 depict consecutive manufacturing steps in
the production of such a printed circuit board element according to
FIG. 1;
[0020] FIG. 5, in a schematic sectional view similar to that of
FIG. 1, shows a modified embodiment of a printed circuit board
element, in which a further waveguide path adjoins the deflection
mirror;
[0021] FIGS. 6, 7 and 8 depict an exemplary embodiment of a
prefabricated deflection mirror, e.g. made of silicon or glass, in
an elevational view, top view and side view, respectively;
[0022] FIGS. 9 and 10, in illustrations similar to the sectional
view of FIG. 1, show cut-outs of two printed circuit board elements
formed with focusing lenses on the exit end of another, vertical
optical waveguide; and
[0023] FIGS. 11 and 12 illustrate two examples of prefabricated
deflection mirrors, i.e. mirrors produced by a molding process on
substrates or carriers.
[0024] FIG. 1 schematically depicts a printed circuit board element
1 with a substrate 2, e.g. a usual FR4 substrate. To this substrate
2 are attached various components in a single operation, FIG. 1
illustrating, by way of example, an optoelectronic component 3 such
as a laser diode, and a passive component in the form of a
deflection mirror 4. These components 3, 4 (as well as other
components not illustrated in detail in the drawing) can be fixed
to the substrate 2 for instance by gluing. It should be mentioned
that FIG. 1 and the following Figures do not show the conductors
required for contacting the components in detail, e.g. 3 and 4,
such as structured copper layers and/or contact bores etc. In this
respect, it is, for instance, referred to WO 2005/064381 A1, the
disclosure of which is to be regarded as included herein by way of
reference.
[0025] Components 3, 4, in the exemplary embodiment according to
FIG. 1, are embedded in a uniform photopolymerizable optical layer
material 5, in which an optical waveguide 6 is, furthermore,
structured by a two- or multi-photon absorption process. This
optical waveguide 6 extends from the optoelectronic component 3,
for instance, as far as to closely in front of the 45.degree.
mirror surface 7 of the deflection mirror 4. However, it is, of
course, also possible, and preferred in many cases, to guide the
optical waveguide 6 directly as far as to the mirror surface 7, as
is the case in the exemplary embodiment according to FIG. 5. Such a
slight distance between the end of the waveguide 6 and the mirror
surface 7 of the deflection mirror 4 as in accordance with FIG. 1
will not raise any problems if the light can be simply deflected to
the upper side (cf. arrow 8) by the deflection mirror 4 through
the--thin--optical material 5. By contrast, a further waveguide
path 6' is provided in the exemplary embodiment according to FIG.
5, for coupling light in or out as will be explained in more detail
below.
[0026] When producing a printed circuit board element 1 according
to FIG. 1, it is proceeded such that an appropriate substrate 2
such as an epoxy resin substrate, e.g. the above-mentioned FR4
substrate, is equipped with the components, i.e., in particular,
the optoelectronic component 3 and the passive component in the
form of the deflection mirror 4, in a single operation. The
components 3, 4 etc. are attached to the substrate 2, particularly
by gluing; such an adhesive connection allows also electrical
contacts to be provided in the region of the optoelectronic
component 3, which is, however, not to be elucidated here. A
substrate thus equipped with components 3, 4 is illustrated in FIG.
2.
[0027] After this, the optical layer 5 of photopolymerizable
material is applied onto the substrate 2, cf. FIG. 3, with the
components 3, 4 previously attached to the substrate 2 being
embedded in this layer 5. The application of the optical layer 5,
which is comprised of a photoreactive polymer, may, for instance,
be realized by casting, doctoring or even spin-coating, as known
per se.
[0028] By photon radiation, the optical material of the layer 5 is
subsequently converted locally in a manner as to have a
comparatively elevated refractive index locally to thereby
structure the desired optical waveguide 6.
[0029] This local conversion of the photoreactive, optical material
5 by the aid of photon beams is schematically illustrated in FIG.
4. From this, a light source 10 such as a laser source is apparent,
which is coupled with a vision unit 11 and has a lens system 12
ahead of it for focusing the emitted laser beam 13 in a focus
region 14 within the optical material 5.
[0030] In detail, during such structuring of the optical material 5
by the aid of the vision or sighting unit 11, for instance, by
departing from the optoelectronic component 3, whose coordinates
are detected, the distances on the sample 1' provided by the
printed circuit board element (to the extent present) are measured,
and the relative movement between said sample 1' and the exposure
system 15 formed by the laser source 10 and the lens system 12 is
controlled not only in the plane of the sample 1', i.e. in the x-
or y-direction, but also in the thickness direction of the sample
1', i.e. in the z-direction, in order to obtain the focus region 14
of the laser beam 13 on the desired site within the optical
material 5. In a preferred manner, the sample 1' is moved in all
three directions x, y and z in order to move the focus region 14 in
the desired manner relative to the sample 1' within the latter and
thereby convert the optical material 5 locally by the photon
radiation; in this manner, the structured optical waveguide 6 is
formed. In the focus region 14, the intensity of the laser light
is, in fact, so high as to induce the known two-photon absorption
process. This process causes the optical material 5 to react
(polymerize) in a manner as to form the optical waveguide 6, which
has a higher refractive index than the optical material 5
surrounding it. Hence results an optical waveguide 6 similar to a
fiber-optic cable, where, in the event of a light transmission by
appropriate reflections of the light at the interface between the
optical waveguide 6 and the surrounding material 5, a bundled light
transmission without important optical losses will be achieved.
[0031] In a subsequent step, an upper printed circuit board layer
(not illustrated) comprising an epoxy resin layer and a copper
outer layer may optionally be applied on the optical material 5, in
particular by pressing, and the steps usually applied for
electrical contacting may be taken; this is conventional per se and
not to be elucidated herein.
[0032] In the present printed circuit board element 1 or 1', the
position of the deflection mirror 4 can also be optically detected
by a sighting unit 11', for which purpose the deflection mirror 4
may carry appropriate marks as will be explained in more detail by
way of FIGS. 6 to 8. The sighting unit 11' may be provided in
addition or as an alternative to the sighting unit 11, or it may be
one and the same--displaced--sighting unit; it is, in particular,
also feasible to provide a two-part sighting unit with a unitary
computation device, for instance in the region of the main sighting
unit 11, so that the complementary sighting unit 11' will then
comprise a suitable connection 16 to said main sighting unit 11,
which connection is entered in dot-and-dash lines. On the other
hand, it is, however, also conceivable to solely provide the
sighting unit 11', with the controls, illustrated by broken lines,
of the laser source 10 and the optics 12 being consequently
provided.
[0033] In the previously described technique, it is of particular
advantage that the orientation of the respective optical waveguide
6 can be adapted in situ, if appropriate reference marks (cf. FIGS.
6 to 8) for the localization of the site for coupling in or out are
provided in three dimensions on the deflection mirror or,
generally, on the components.
[0034] FIG. 5 depicts a printed circuit board element 1 which is
substantially configured in a manner similar to that of FIG. 1, yet
differs from the latter in that the optical waveguide 6 extending
parallely with the plane of the printed circuit board element 1 is
guided directly as far as to the mirror surface 7 of the deflection
mirror 4, with a further optical waveguide path 6' having been
structured from said mirror surface 7 vertically upwards to the
upper face of the printed circuit board element, 1A. This is
possible without any problem with the present printed circuit board
element 1 and makes subsequent mechanical finishing procedures
superfluous, since each of the waveguides 6 and 6' can be
positioned directly at the optical components 4 (and also 3) in a
highly precise manner by photon structuring, and because
structuring in the z-direction (cf. FIG. 4) is also readily
possible by such photon structuring. In this manner, the embodiment
according to FIG. 5 allows for the deflection of light from the
plane of the optical position (and into the plane of the optical
position, respectively).
[0035] The deflection mirror 4 may, for instance, be prefabricated
from silicon or glass with a metal coating, and as is apparent from
the drawing, particularly from FIGS. 6 to 8, it is preferably
comprised of a prismatic body having, e.g., a slanted (cf. FIGS. 6
and 9 to 11) or concave (cf. FIG. 12) front surface 7' to form a
mirror surface 7 or the reflection field for the light in the
waveguide 6 (cf. FIG. 1 or 5). In the exemplary embodiment
illustrated, this is a 45.degree.-deflection mirror 4 such that the
light beam is deflected by a total of 90.degree. from the plane of
the printed circuit board element 1 in a direction perpendicular to
the same (or vice versa), as is also apparent from FIGS. 1 and 5.
The prefabricated deflection mirror 4 may comprise different marks
for the positioning of the laser beam 13 or focal point 14 during
the structuring of the optical waveguides 6 and 6, respectively.
Thus, for instance, according to FIG. 7, marks are provided on the
plane upper side 17 of the deflection mirror 4 for determining the
position, or a possible rotation, of the deflection mirror 4 via
the sighting unit 11' (cf. FIG. 4). Furthermore, a reflective field
18 may be provided on the upper side 17 of the deflection mirror 4
for determining the z-position of the deflection mirror 4 via the
reflection of the measuring laser in the sighting unit 11'.
[0036] In addition to, or instead of, the above, it is also
possible to provide position marks 19, 20 and 21 at the front
surface 7' in the region of the mirror surface 7 in order to enable
the determination of the position of the front surface of the
deflection mirror 4 via the sighting unit 11'. The position marks
19, 20 and 21 are, above all, provided to recognize deviations of
the slant (in the event of a plane mirror surface 7) or of the
curved surface (in the event of a spherical or aspherical mirror 7)
from the desired position, such deviations being, for instance,
caused by production inaccuracies or insertion inaccuracies. When
scanning the position marks 19, 20, 21, it will then be possible to
appropriately react to such deviations by adapting the angle of
impingement of the optical waveguide 6 and/or 6' on the mirror
surface 7 such that the light beam guided through the structured
optical waveguide 6 and/or 6' will be optimally reflected from the
deflection mirror 4 upwardly or towards the optoelectronic
component 3.
[0037] An advantage of the present technology resides in that the
deflection mirror 4 can be attached to the printed circuit board
substrate 2 simultaneously with the optically active components
3.
[0038] What is also advantageous is the use of the photon process
for structuring the waveguide 6, 6' in the photopolymerizable
optical material 5 in which the components 3, 4 are embedded,
wherein it is feasible, particularly by the aid of the sighting
unit 11, 11', to detect both the position of the deflection mirror
4 per se and a possible rotation or tilting as may occur during the
automatic insertion process; this will enable an appropriate
adaptation and exact orientation when structuring the optical
waveguide 6, 6' such that no extreme preciseness is previously
required for the insertion process. The measuring laser beam of the
sighting unit 11, 11' also allows for the precise
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